There are, notably in the transport field, an increasing number of onboard systems comprising a plurality of actuators distributed in a structure, sometimes in large numbers. The development of actuators of ever smaller dimensions allows a better integration of the latter and hence an increase in their number within a given system. In the aviation field, for example, it is desirable that an ever increasing number of actuators of various types are used in aircraft in order to allow an optimized management of the flight by precisely located actions. The said actuators are activated on the basis of measurements originating from a plurality of sensors of physical parameters. These sets of sensors and actuators participate in the flight of the aircraft by optimizing the energy budget amongst other functions. Finally, a second set of sensors monitors the detailed state of health of the vehicle in real time, usually called “health monitoring”; in this case, the sensors participate in heightening the safety of the flight and in optimized maintenance operations. Therefore, a developed aircraft wing is designed to contain a large population of items of microequipment dispersed throughout the latter. Such a wing may specifically comprise a plurality—several tens or even hundreds—of microactuators making it possible to supervise the air flows at precise points of the wing surface. In this way, a turbulent air flow located on a portion of the wing surface, detected by a sensor provided for this purpose, can be corrected as a laminar flow, by means of one or more microactuators situated close by.
There now follows a description of actuator types chosen as examples in order to clearly describe the invention: boundary-layer actuators. The invention can be applied with all types of known or future actuators, provided that the said actuators have a physical effect the thermal and/or acoustic signature of which can be measured, as is explained in greater detail below.
The abovementioned microactuators can for example be fluid microactuators, also commonly known by the name Plasma Synthetic Jet Actuators or by the corresponding acronym “PSJA”. PSJA actuators take the form of small cavities containing a plasma, an electric arc heating the content of the cavity in order to produce a discharge of the air contained in the cavity, followed by an expansion. PSJA actuators can take the form of discrete components, or else the form of components of the micro-electromechanical systems type commonly called “MEMS”, that is to say components that are micro-machined, for example in a collective manner with other components or circuits.
A PSJA actuator can be activated periodically with a certain frequency for the purpose of emulating a mechanical-vortex generator. The air exits and then enters a PSJA actuator in an alternating manner, which disrupts the air flow in its vicinity, making it possible to reduce the separation of the boundary layer. It is also possible to cite piezoelectric microactuators assembled in sets, and distributed over the wing surface, that are capable of generating a deformation of the surface of the latter on request.
It is possible also to cite MEMS micromotor-based microactuators, or else shape-memory alloy actuators or actuators of the artificial muscles type.
It should be noted that a system may comprise a plurality of items of equipment of one of the aforementioned types, but equally a heterogeneous plurality of sensors of various types.
It is desirable, for example, for a wing comprising a plurality of microactuators of the aforementioned types, that the partial or total failure of each of the actuators to be able to be detected. Specifically, the failure of a single actuator may have unfortunate consequences with respect to the aerodynamic flow around the whole surface of the wing, a contamination effect being able to rapidly extend an initially localized turbulent flow to the whole of the wing surface.
It is possible to attach to each microactuator an integrated monitoring device directly measuring the correct operation of the actuator. Nevertheless, such a solution may be detrimental in practice, because:                1) it supposes an increasing complexity of the microactuators;        2) such an increasing complexity notably brings with it an excessive cost of the monitoring function relative to the cost of the microsystem to which it is fitted;        3) the addition of an integrated monitoring device can be detrimental in terms of space requirement, the monitoring device necessarily providing a significant space requirement;        4) in the same way, the addition of a monitoring device to each microactuator results in a greater weight, which is detrimental to the flight performance of the aircraft;        5) each monitoring device has to be powered;        6) in any case, it is necessary to use a connection system that is made more complex in order to connect each monitoring device electrically and functionally to the associated microactuator, and the microsystems thus formed with a centralized management device;        7) each monitoring device itself has a susceptibility with respect to the environment; and        8) the quality of coverage of the test by the said integrated monitoring device is usually limited, only certain members of the actuator being monitored rather than the effective course of its action by its physical consequences.        